Ecology and the Environment

• Habitat is the place where an organism lives e.g. a rocky shore or a field.
• Population is all the organisms of one species in a habitat.
• Community is all the different species in a habitat
• Ecosystem - all the organisms living in a particular area and all the non-living conditions, e.g. temperature, climate, soil-type
• Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem.
• High biodiversity is important as it make sure that ecosystems are stable because different species depend on each other for things like shelter and food. Different species can also help to maintain the right physical environment for each other.
• Lots of human actions, including deforestation, pollution as well as global warming are reducing biodiversity.
• Environmental changes are caused by living or non-living factors and they affect communities in different ways, some populations may increase, some may decrease.
• Some non-living conditions that affect communities could include light intensity, moisture level and soil pH. Toxic chemicals can lead to killing the death of organisms as organisms can receive a toxic dose.
• Living factors (availability of food, number of predators and competition)
• you can use a quadrat to study the population size of small organisms. You can do this by placing a 1m^2 on the ground at a random point within the first sample area. Count all the organisms you're interested in within the quadrat. repeat steps 1 and 2. work out the mean number of organisms per quadrat within the first sample area.
• to work out the population size of an organism in one sample area you need to work out the mean number of organisms per m^2. then just multiply the mean by the total area of the habitat.
• Food chains always start with a producer e.g. a plant. Producers make their own food using energy from the Sun.
• Producers are eaten by primary consumers. Primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers.
• All these organisms eventually die and get eaten by decomposers e.g. bacteria. Decomposers break down dead material and waste.
• Each stage is called a trophic level.
• A pyramid of numbers has each bar on a pyramid shows the number of organisms at this stage of the food chain. Sometimes the pyramid of numbers is not a pyramid at all as 1 fox may feed 500 fleas.
• Each bar on a pyramid of biomass shows the mass of living materials shows the mass of living material at that stage of the food chain. SO the one fox would have a big biomass and the hundreds of fleas have a very small biomass. Biomass pyramids are practically always the right shape.
• Pyramids of energy show the energy transferred to each trophic level in a food chain. e.g. when a rabbit easts a dandelion it gets energy, which the dandelions got from the Sun.
• energy is transferred along a food chain.

  1. energy from the Sun is the source of energy for nearly all life on Earth.
  2. plants use energy from the Sun to make food during photosynthesis. This energy then works its way through the food chain as animals eat plants and each other.
• 3. not all the energy that's available to the organisms in a trophic level is passed on to the next trophic level - around 90% of then energy is lost in various ways.
• 4. some parts of food aren't eaten by organisms so the energy isn't taken in. some parts of food are indigestible (e.g. fibre) so pass through through organisms and come out as waste.
• 5. a lot of the energy that does get taken in is used for stating alive (e.g. respiration) which powers all life precesses.

  6. most of this energy is eventually transferred to the surroundings by heat. Only 10% of the total energy available becomes biomass which is the energy that's transferred from one trophic level to the next.
• Foods webs show how the food chains are linked.
• Materials that organisms need to survive, such as carbon and nitrogen are constantly recycled through both biotic and abiotic components of ecosystems.
• when fossil fuels are burnt without enough air supply they produce the gas carbon monoxide (CO). It's a poisonous gas that combines with haemoglobin in red blood cells, it prevents them from carrying oxygen.
• Carbon monoxide is mostly released in car emissions but most modern cars are fitted with catalytic converters that turn carbon monoxide into carbon dioxide, decreasing the amount of carbon monoxide that's released into the atmosphere.
• Acid rain is caused by sulphur dioxide and nitrogen oxide. Sulphur dioxide comes from sulfur impurities in fossil fuels and nitrogen oxide is produced by the burning of fossil fuels.
• When sulfur dioxide and nitrogen oxide mixes with rain clouds it forms dilute sulphuric acid and nitric acid. This then falls as acid rain.
• The main causes of acid rain is internal combustion engines in cars and power stations.
• Acid rain can causes a lake to become more acidic. This has a severe effect on the lakes ecosystem as many organisms are sensitive to changes in the pH and can't survive in more acidic conditions. Many plants and animals die.
• Acid rain can also kill trees. The acid rain damages leaves and releases toxic substances from the soil, making it hard for the trees to take up nutrients.
• the temperature of the earth is a balance between the energy it gets from the Sun and the energy it radiates back out into space.
• 1. Gases in the atmosphere absorb most of the heat that would would normally be radiated out into space and re-radiate it in all directions. This is the greenhouse effect.
• If the gases didn't absorb the heat then at night there'd be nothing to keep energy in, and we would very quickly get very cold.
• The greenhouse gases are the different gases in the atmosphere that keep any energy in. They include water vapour, carbon dioxide and methane.
• By humans increasing the amount of carbon dioxide and other greenhouse gases. It enhances the greenhouse effect.
• By a result of the increase of greenhouse gases, the Earth is heating up which is called global warming. It is a type of climate change and causes other types of climate change e.g. changing rainfall patterns.
• Climate change could lead to extreme weather, rising sea levels and flooding due to the polar ice caps melting. This could cause habitat loss and could affect food webs and crop growth.
• Humans releases carbon dioxide in everyday activities such as in car exhausts, industrial processes as we burn fossil fuels. By cutting large areas of forest (deforestation) for timber and to clear land for farming and this activity affects the level of carbon dioxide in the atmosphere.